Controlled Architecture of Hybrid Polymer Nanocapsules with Tunable Morphologies by Manipulating Surface-Initiated ARGET ATRP from Hydrothermally Modified Polydopamine

This study presents a facile hydrothermal approach in a "Tris" buffer solution for fabricating polydopamine (PDA) nanostructures with different morphologies (core-shell, yolk-shell, and hollow spheres), while concurrently tuning their stability, permeability, and reactivity. Structural and morphological transformation of PDA induced by hydrothermal treatments is described in detail. Surface initiated growth of poly(N-isopropylacrylamide) (PNIPAM), a thermally responsive polymer, was then achieved from the hydrothermally treated PDA by using the activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Interestingly, inward and outward growth of polymer chains from PDA hollow spheres could be manipulated depending on the solvation effect and hydrothermally induced regulation of the pore network in the PDA structure. Hybrid PDA/PNIPAM nanocapsules with tunable morphologies could be obtained. This study provides new insights into PDA's structural evolution under hydrothermal treatments and develops a promising strategy by combining the bioinspired PDA chemistry with ARGET ATRP, an environmentally friendly and easily operated polymerization technique, to prepare stimulus-responsive nanocapsules that would be potentially used in biological and biomedical areas.